[1] Birla Inst Technol, Dept Appl Chem, Ranchi 835215, Bihar, India
[2] Univ Witwatersrand, Microscopy & Microanal Unit, ZA-2050 Johannesburg, South Africa
[3] Univ Witwatersrand, Sch Chem, Inst Mol Sci, ZA-2050 Johannesburg, South Africa
[4] MINTEK, Adv Mat Div, ZA-2125 Randburg, South Africa